Deep drawn heat exchanger



3, 1961 w. G. REYNOLDS 2,994,946

DEEP DRAWN HEAT EXCHANGER Filed Feb. 27, 1956 2 Sheets-Sheet V 33b 3 28 Q A Fl FIG. 8

\ Q47 4 I INVENTOR. 4 4 g1 WILLIAM G. REYNOLDS A ATTORNEY g- 3, 1961 w. G. REYNOLDS 2,994,946

DEEP DRAWN HEAT EXCHANGER Filed Feb. 27, 1956 l 2 Sheets-Sheet 2 INVENTOR.

WiLLlAM G. REYNOLDS act/MW ATTORNEY United States Patent F 2,994,946 DEEP DRAWN HEAT EXCHAN GER William G. Reynolds, Anchorage, Ky., assignor to Reynolds Metals Company, Louisville, Ky., a corporation of Delaware Filed Feb. 27, 1956, Ser. No. 567,878 3 Claims. (Cl. 29157.3)

The present invention relates to heat exchangers in the form of drawn vessels.

The principal objects of the present invention are: to provide a heat exchanger of novel form which can be produced inexpensively; and to provide one in the form of a deep drawn pressure welded passageway panel incorporating at least one system of interior channels or passageways which accommodates the flow of at least one fluid through the deep drawn walls of the heat exchanger.

According to the present invention, a fiat blank or panel is produced by roll bonding two or more sheets of metal, such as aluminum, in face to face relation, with a weldresist pattern between adjacent faces, this pattern defining a potential system of channels or passageways. The resulting composite panel is deep drawn to a suitable bucket shaped form and then expanded by internal pressure to form one system of internal passageways conforming to the design of the weld-resist pattern. The present invention demonstrates the ease with which drawn sheets may be provided with a system of passageways and thus made to function as heat exchangers or heat exchange walls while such shapes otherwise perform their normal functions. Furthermore, the expansion of these passageways works the metal forming the passageways and thus strengthens them and has the effect of reinforcing the wall of the drawn member.

The invention is illustrated in the accompanying drawings wherein:

FIGURE 1 is a partly broken plan view of a blank for a pressure welded passageway panel;

FIGURE 2 is a section taken along line 22 of FIG- URE 1;

FIGURE 3 is a partly broken fragmentary view of a pressure welded passageway panel before expansion;

FIGURES 4, 5 and 6 illustrate successive steps in the first stage of the drawing operation wherein the fiat panel is drawn to a preliminary bucket shape;

FIGURES 7, 8 and 9 illustrate successive steps in the second and last stage of the drawing operation wherein the preliminary bucket shape is deep drawn to a final bucket shape;

FIGURE is a vertical sectional View taken through the expansion apparatus dies with the bucket shaped member in place;

FIGURE 11 is a partly broken side elevation of 'the final product; and

FIGURE 12 is a partly broken side elevation of a similar product.

The product shown in FIGURE 11 involves the performance of three operations, namely: pressure welding; drawing; and expanding.

Pressure welding In performing the pressure welding operation, two foreshortened metal sheets 1 and 2 are superposed one upon the other with a foreshortened stop weld pattern of appropriate design interposed between them as indicated in FIGURES 1 and 2. These superposed sheets are then pressure welded together to form the square unexpanded panel 3 of FIGURE 3.

Any appropriate stop weld pattern may be used. In the present case, circular passageways extending horizontally through the sides of the bucket and connected Patented Aug. 8, 1961 with cross passageways extending across the bottom of the bucket are desired; hence, the foreshortened resist pattern shown in FIGURE 2 comprises: a series of concentric oval-shaped resist areas 5, 6 and 7; a centrally disposed resist area 8 extending along the minor axis of the ovals and completely across all ovals; and a pair of T-shaped areas, one on each side of the minor axis 8, each T-shaped area including a stem area 9 along the major axis of the ovals and a cross head area 10 at right angles to the stem area. In addition to this, the outermost oval is provided, at one end of its long axis, with a laterally directed resist area 11 extending to the adjacent edge of the panel and, at its opposite end, with another like resist area 12 extending part way toward but stopping short of the adjacent edge of the panel.

It will be understood that, in pressure welding the sheets 1 and 2, they may be roll bonded as explained in the Long patent, #2,662,273, using the pressures applicable to aluminum where aluminum sheets are employed. This involves reducing the thickness of the original blank, formed by the sheets 1 and 2, to a value as much as onefourth or one-fifth of the value of their original thickness and correspondingly elongating the sheets and the resist patterns. When most of the thickness reduction is accomplished in one pass through the rolls, the sheets will be welded together at all areas except those containing the resist material and they thus form a composite but unexpanded sheet metal panel 3.

This panel will, of course, be square in outline in this particular case.

Drawing operation It will be observed that the fiat panel of FIG. 3 is marked with center, intermediate and outer circles 14, 15 and 16. The area, which lies inside of circle 14, represents the flat bottom 17 of the finished heat exchanger. The area, which lies outside of circle 14 but within circle 15, represents the curved bottom shoulder portion 18 lying between the bottom wall 17 and the side wall 19. The area which lies outside of circle 15 and inside of the outer circle 16 represents the side wall 19 while the area, which lies outside of the side wall 19, represents the flange 20.

When the flat panel is drawn into the shape of a bucket, the bottom shoulder 18, between circles 14 and 15, will be curved upwardly and that portion, which is curved, will be circumferentially contracted. In other words, the diameter of circle 15 in the drawn product will be smaller than it was in the panel. The side wall area between circles 15 and 16 will be similarly contracted with the diameter of circle 16 being reduced to that of the contracted circle 15. Naturally the area outside of circle 16 will also be circumferentially contracted.

These contractions tend to thicken the corresponding wall sections of the final product while the drawing operation, by stretching such wall sections axially, tend to reduce their respective thicknesses. These opposing tendencies may be balanced against each other so as to have the thickness of any wall section either remain the same or change in the desired direction. For example, to keep the thickness, of the side wall area, the same in the product as it was in the panel, the side wall section must be stretched axially so as to increase the axial distance between circles 15 and 16 of the product to a value greater than that of the radial distance between circles 15 and 16 of the panel and this increase in the axial dimension must be controlled to equal the decrease in the radial dimension. This is, of course, a matter of die design.

In performing the drawing operation, the panel 3 is interposed between and clamped by a pair of upper and lower drawing dies 21 and 22. The lower die 22 is bored with a ram hole 23 and provided at the upper edge of the bore with a rounded shoulder 24 to flare the upper bondedportions to expand outwardly into flattening conend of the bore. A ram 25 is provided to deform and draw the panel 3.

In FIGURE 5, which illustrates an intermediate stage of this drawing operation, the panel 3 has been dished to the shallow bucket shape indicated at 33c. In reaching this intermediate stage, the margins of the panels slip inwardly from their original position between dies 21 and 22. This slippage is controlled to effect or cause the dies to calendar the panel 3 so that it may contract to the cylindrical shape desired without creasing and wrinkling.

It will be understood, of course, that the drawing operation does not stop at FIGURE 5 but continues to the final product of the first stage which is shown in FIGURE 6. Here the upper portion of the panel has moved entirely from between the dies and the deeper cup shape 33b is the final shape reached in the first stage of the drawing operation.

In the drawing operation, there is a maximum ratio between the diameter of the blank and the drawn diameter that can be produced in one drawing operation. Where the final product exceeds this ratio, a second drawing operation is necessary and, in the present case, it is illustrated in FIGURES 7-9.

The dies of FIGURES 7-9 are similar to those of 46 in that they include an upper die 27, a lower die 28 having a ram hole 29 and a bore shoulder 30 and a ram 31. In this operation, the diameter of the ram 31 is smaller than that of the bucket 33b; hence, a calendering ring 32 is placed around ram 31 and within the bucket 33b. As the ram 31 pushes the bucket into the hole 29, the ring 32 calendars the metal to allow it to flow without creasing or wrinkling. This ring '32 is held in place by any suitable clamping mechanism.

As this drawing operation proceeds, the shape of the bucket changes from that indicated at 33b at FIG. 7 to 33a in FIG. 8 and finally to the shape 33 shown in FIG. 9, at the finish of this second stage drawing operation. In FIG. 9 the cup is formed to its final shape and size; hence, it has a bottom 17, a rounded bottom shoulder 18, a side wall 19 and flange 20. When the bucket is removed from the die of FIGURE 9, its flange flattened and trimmed, it is ready for the expansion operation.

Expansion The flat mouth 11 of the bucket at the edge of flange 20 is first forced opened by a suitable tool and a tubular fluid connector 35 is wedged into the mouth 11. The expansion dies are assembled after the bucket is either fitted over the inner or male die 36 of the expansion apparatus or placed within the outer or female die 37 with its flange 20 resting on the upper end of the outer die and with its tubular fluid connection 35 aligned with a suitable recess in both dies. When the dies 36 and 37 are assembled, the outer surface of the bucket 33 is spaced, from the adjacent surface of the outer die 37,

a distance equal to the degree of passageway expansion desired.

It may be desirable to provide the outer die with a fluid connection 38 extending from the expansion space provided between the outer die and the unexpanded bucket and to fill this space with a holding liquid under pressure before performing the internal expansion operation. The use of a holding pressure, which is described and claimed in the Thomas application, Ser. No. 511,358, is preferred because it tends to pin the bonded areas of the bucket firmly against the inner die 36 while permitting the unbonded portions of the bucket to expand outwardly into the holding medium. Consequently, a holding pressure of 600 psi. may be introduced to the space between the bucket and the outer die and then an expansion pressure of 3000 psi. (2400 psi. higher) introducedthrough the fluid connector 35 into the unbonded passageway forming portions of the bucket.- This will cause these untact with the adjacent outer surface of the die thus forming the passages indicated in FIG. 11. Holding pressures higher than 600 p.s.i., with correspondingly higher in ternal expansion pressures, usually give better results.

When the expansion of the passageways has been completed, the product is disconnected from the expansion fluid system, removed from the dies and further processed conventionally in the manner required to fit it for its intended use. This may require the application of permanent fluid connections (not shown) to the laterally directed passageways 11 and 12.

FIGURE 12 illustrates a heat exchange vessel 40 made by deep drawing a passageway panel having a resist pattern designed to provide one lone passageway 41 extending spirally along the cylindrical side wall and expanded on both sides of that wall. A vessel of this character may be used as a heat exchanger for an automobile power steering mechanism. In this case, cooling fluid would be circulated in a conventional manner within the vessel 40. Inlet and outlet connectors 42 and 43 are, of course, welded to the vessel 40 at opposite ends of the passageway 41.

While each of the products of FIGS. 11 and 12 is made from a two sheet panel which accommodates the flow of only one fluid within the confines of its wall, it will be understood that the panel may, if desired, be designed to accommodate the flow of one or more other fluids. Also, more than two sheets may be employed. For example, three foreshor-tened sheets with two fore-shortened weld-resist patterns may be pressure welded and drawn to form a hollow heat exchanger whose wall internally accommodates the flow of two different fluids.

Since the product of FIG. 11 is expanded on its outer side while that of FIG. 12 is expanded on both inner and outer sides, it will be understood that products, made in accordance with this invention, may be expanded on the inside only.

Having described my invention, I claim:

I. A method of making a heat exchanger comprising: providing a composite sheet metal pressure-welded passageway panel containing a pattern of internal unbonded and unexpanded potential-passageway-forming portions; deep drawing said panel into an integral bucket-shaped seamless member having a side wall of general cylindrical shape containing said unbonded portions and an end wall; and expanding unbonded portions of said side wall by introducing a fluid under pressure into such portions to provide said side wall with internal passageways.

2. The method of claim 1 wherein: the introduction of fluid under pressure into said side wall is carried out with said member positioned between interfitted corresponding male and female dies having a spacing between their facing surfaces equaling the thickness of the expanded passageway portions in the heat exchanger produced.

3. The method of claim 2 wherein: the expansion of said unbonded portions is substantially limited to one face of said side wall of said seamless member by conducting said expansion with said side Wall interposed between dies, one of which cooperates with said one face to form a shallow chamber into which said one face may be expanded and the other of which has flush engagement with the other face of said side wall, and introducing a holding fluid into said chamber and maintaining that fluid under pressure so as to press and hold said other face of said side wall in flush engagement with said other die during said expansion.

Muffly Apr. 23, 1929 Scull June 24, 1930 (Other references on following page) 5 UNITED STATES PATENTS Dake June 1, 1937 Sandler May 17, 1938 Sendzimir Aug. 20, 1940 Booth Aug. 27, 1940 M ilborn Apr. 10, 1951 Clay Feb. 26, 1952 Raskin Jan. 20, 1953 Kranenberg Aug. 18, 1953 6 Smith Mar. 30, 1954 Grenell Sept. 28, 1954 Simmons Apr. 3, 1956 Adams Oct. 16, 1956 Rieppel et a1 Jan. 29, 1957 Grenell Aug. 5, 1958 Staples Dec. 30, 1958 

